﻿using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;

namespace AesEncrypt
{
    /// <summary>
    /// Aes加密算法适用于固定的加解密
    /// </summary>
    public static class AesEncrypt
    {
        /// <summary>
        /// 对称算法的密钥
        /// </summary>
        private readonly static byte[] aesKey = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32 };
        /// <summary>
        /// 对称算法的初始化向量
        /// </summary>
        private readonly static byte[] aesIV = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 };


        /// <summary>
        /// 加密
        /// </summary>
        /// <param name="Text">被加密的字符串</param>
        /// <returns>Base64</returns>
        public static string Encrypt(string Text)
        {
            byte[] encrypted;
            encrypted = EncryptStringToBytes_Aes(Text, aesKey, aesIV);
            return Convert.ToBase64String(encrypted);
        }


        private static byte[] EncryptStringToBytes_Aes(string plainText, byte[] Key, byte[] IV)
        {
            // Check arguments.
            if (plainText == null || plainText.Length <= 0)
            {
                throw new ArgumentNullException("plainText");
            }
            if (Key == null || Key.Length <= 0)
            {
                throw new ArgumentNullException("Key");
            }
            if (IV == null || IV.Length <= 0)
            {
                throw new ArgumentNullException("IV");
            }
            byte[] encrypted;
            // Create an Aes object
            // with the specified key and IV.
            using (Aes aesAlg = Aes.Create())
            {
                aesAlg.Key = Key;
                aesAlg.IV = IV;

                // Create a decrytor to perform the stream transform.
                ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);

                // Create the streams used for encryption.
                using (MemoryStream msEncrypt = new MemoryStream())
                {
                    using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
                    {
                        using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
                        {

                            //Write all data to the stream.
                            swEncrypt.Write(plainText);
                        }
                        encrypted = msEncrypt.ToArray();
                    }
                }
            }
            // Return the encrypted bytes from the memory stream.
            return encrypted;
        }


        /// <summary>
        /// 解密
        /// </summary>
        /// <param name="text">被Aes加密后的Base64</param>
        /// <returns>字符串</returns>
        public static string Decrypt(string text)
        {
            string roundtrip;

            byte[] myByte = Convert.FromBase64String(text);
            roundtrip = DecryptStringFromBytes_Aes(myByte, aesKey, aesIV);

            return roundtrip;
        }
        private static string DecryptStringFromBytes_Aes(byte[] cipherText, byte[] Key, byte[] IV)
        {
            // Check arguments.
            if (cipherText == null || cipherText.Length <= 0)
            {
                throw new ArgumentNullException("cipherText");
            }
            if (Key == null || Key.Length <= 0)
            {
                throw new ArgumentNullException("Key");
            }
            if (IV == null || IV.Length <= 0)
            {
                throw new ArgumentNullException("IV");
            }
            // Declare the string used to hold
            // the decrypted text.
            string plaintext;

            // Create an Aes object
            // with the specified key and IV.
            using (Aes aesAlg = Aes.Create())
            {
                aesAlg.Key = Key;
                aesAlg.IV = IV;

                // Create a decrytor to perform the stream transform.
                ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);

                // Create the streams used for decryption.
                using (MemoryStream msDecrypt = new MemoryStream(cipherText))
                {
                    using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
                    {
                        using (StreamReader srDecrypt = new StreamReader(csDecrypt))
                        {

                            // Read the decrypted bytes from the decrypting stream
                            // and place them in a string.
                            plaintext = srDecrypt.ReadToEnd();
                        }
                    }
                }
            }
            return plaintext;
        }
    }
}
